The most common system for lighting office, commercial, and industrial space is overhead lighting. Conventional overhead lighting normally uses tubular fluorescent lamps, incandescent lamps, or HID lamps as a light source. In many applications, the light which radiates from the lamps is passed through a louver which is effective to focus and direct the radiating light downwardly.
A louver is a grid-like structure comprising perpendicularly intersecting blades. The louver may be formed in one piece of plastic or it may be assembled from multiple pieces formed of aluminum, for example.
A louver which is made of aluminum can readily be used with either fluorescent lamps, which give off relatively little heat, or with incandescent or HID lamps, which may give off substantial amounts of heat. On the other hand, plastic louvers tend to deteriorate if subjected to the heat of incandescent or HID lamps.
Regardless of whether louvers are molded of plastic or formed of aluminum, the blades preferably have parabolic surfaces defining their primary reflective surfaces. These parabolic surfaces are vertically elongated and serve to enhance the light reflection characteristics of the louver as it modifies light emitted from the lamps above the louver.